As mentioned below, various production methods have been disclosed for industrially useful amide compounds.
Recently, there have been discovered nitrile hydratases having a nitrile hydration activity capable of converting a nitrile group into an amide group through hydration and there has been already disclosed a method for producing a corresponding amide compound from a nitrile compound by the use of the enzyme, a microbial cell containing the enzyme, or the like. The production method is known to have benefits such as a high conversion and a high selectivity from the nitrile compound to the corresponding amide compound, compared to the conventional scientific methods.
In industrially producing an amide compound by using these nitrile hydratases, it is important to maximize the amide compound productivity of the nitrile hydratases as catalysts (the number of molecules of the amide compound produced per one molecule of the nitrile hydratase). For this reason, numerous proposals have been made for the purposes of maintaining and increasing the enzyme activity, preventing the activity deterioration, recovering the deteriorated enzyme activity and the like. For example, it is well known that the enzyme activity is maintained and increased by contacting a microbial cell containing a nitrile hydratase or a processed product of the microbial cell with an oxidant in the conditions where the cells are not allowed to grow (see Patent Document 1). Further, it is well known that the activity deterioration of a nitrile hydratase is prevented by using a nitrile compound in which the concentration of the contained hydrocyanic acid is reduced (see Patent Document 2). In addition, there are known a method in which the reaction is carried out by using a microbial cell crosslinked with glutaraldehyde (see Patent Document 3), a method in which the reaction is carried out in the presence of a higher unsaturated fatty acid or its salt (see Patent Document 4), a method in which the reaction is carried out by using a microbial cell processed with an organic solvent or a processed product thereof (see Patent Document 5), and the like. The above is the background art of the first invention.
Further, as mentioned above, one of the main methods for producing acrylamide is a method of hydrating acrylonitrile. For example, there is known a method of hydrating acrylonitrile with a metallic copper catalyst such as Raney copper or the like or a method of hydrating acrylonitrile by using a microbial cell containing a nitrile hydratase, a processed product of the microbial cell, or the like as a catalyst.
Among these, as an industrial production method, the method for producing acrylamide using the microbial cell containing the nitrile hydratase or the like as a catalyst, has attracted attention because the method has a high conversion and a high selectivity of acrylonitrile, compared to the conventional method of hydration using the metallic copper catalyst and the like.
In order to efficiently produce acrylamides with higher quality by using the microbial cell containing the nitrile hydratase, and the like as a catalyst, impurities inhibiting the catalytic action of the microbial cell and the like are required to be removed as much as possible.
In addition, acrylamides obtained by such reactions are mainly used as a raw material for an acrylamide-based polymer. However, recently a further improvement of the quality is required for the acrylamide-based polymer. For example, the applications of an acrylamide-based polymer include a flocculant. Recently, the acrylamide-based polymer used as a flocculant is expected to have a higher molecular weight while maintaining the water solubility to improve the performance. Further, the acrylamide-based polymer is used as an additive for manufacturing paper, and the like, and, as the additive for manufacturing paper, a polymer being more excellent in hue is required in order to further improve the quality of the resulting paper.
As a method for improving the quality of the acrylamide obtained with use of cellular catalysts containing the nitrile hydratase, and the like or the quality of the polyacrylamide, as mentioned above, there are known a method in which the concentration of hydrocyanic acid in a nitrile compound is reduced by a chemical process and then the nitrile hydratase is allowed to act on the nitrile compound to produce an amide compound (for example, see Patent Document 2), and a method in which oxazole and hydrocyanic acid contained in acrylonitrile as impurities are reduced and then the acrylonitrile is converted into acrylamide, followed by producing an acrylamide-based polymer from the acrylamide (for example, see Patent Document 6). The above is the background art of the second invention.    [Patent Document 1] Japanese Patent Application Laid-Open Publication No. 2004-350573    [Patent Document 2] Japanese Patent Application Laid-Open Publication No. 11-123098    [Patent Document 3] Japanese Patent Application Laid-Open Publication No. H7-265091    [Patent Document 4] Japanese Patent Application Laid-Open Publication No. H7-265090    [Patent Document 5] Japanese Patent Application Laid-Open Publication No. H5-308980    [Patent Document 6] International Publication WO 2004/090148